Apparatus for monitoring and controlling peritoneal dialysis

ABSTRACT

A dialysis apparatus includes a housing; a first electrical contact carried by the housing; a hydrogel material located within the housing; a second electrical contact connected to the hydrogel material, the hydrogel material located so as to be contacted by a liquid flowing through the housing; and wherein the hydrogel material expands as the material absorbs the liquid such that the second electrical contact is moved and eventually engage the first electrical contact.

BACKGROUND

The present disclosure relates to medical fluid delivery and inparticular to peritoneal dialysis fluid delivery.

Due to disease or other causes, a person's renal system can fail. Inrenal failure of any cause, there are several physiologicalderangements. The balance of water, minerals and the excretion of dailymetabolic load is no longer possible in renal failure. During renalfailure, toxic end products of nitrogen metabolism (urea, creatinine,uric acid, and others) can accumulate in blood and tissues.

Kidney failure and reduced kidney function have been treated withdialysis. Dialysis removes waste, toxins and excess water from the bodythat would otherwise have been removed by normal functioning kidneys.Dialysis treatment for replacement of kidney functions is critical tomany people because the treatment is life saving. One who has failedkidneys could not continue to live without replacing at least thefiltration functions of the kidneys.

One type of dialysis is peritoneal dialysis. Peritoneal dialysis uses adialysis solution or “dialysate”, which is infused into a patient'speritoneal cavity through a catheter implanted in the cavity. Thedialysate contacts the patient's peritoneal membrane in the peritonealcavity. Waste, toxins and excess water pass from the patient'sbloodstream through the peritoneal membrane and into the dialysate. Thetransfer of waste, toxins, and water from the bloodstream into thedialysate occurs due to diffusion and osmosis, i.e., an osmotic gradientoccurs across the membrane. The spent dialysate drains from thepatient's peritoneal cavity and removes the waste, toxins and excesswater from the patient. This cycle is repeated.

There are various types of peritoneal dialysis therapies, includingcontinuous ambulatory peritoneal dialysis (“CAPD”) and automatedperitoneal dialysis (“APD”). CAPD is a manual dialysis treatment, inwhich the patient connects an implanted catheter to a drain and allows aspent dialysate fluid to drain from the patient's peritoneal cavity. Thepatient then connects the catheter to a bag of fresh dialysate andmanually infuses fresh dialysate through the catheter and into thepatient's peritoneal cavity. The patient disconnects the catheter fromthe fresh dialysate bag and allows the dialysate to dwell within thecavity to transfer waste, toxins and excess water from the patient'sbloodstream to the dialysate solution. After a dwell period, the patientrepeats the manual dialysis procedure.

In CAPD the patient performs several drain, fill, and dwell cyclesduring the day, for example, about four times per day. Each treatmentcycle typically takes about an hour. APD is similar to CAPD in that thedialysis treatment includes a drain, fill, and dwell cycle. APDmachines, however, perform three to four cycles of peritoneal dialysistreatment automatically, typically overnight while the patient sleeps.Like CAPD, APD machines connect fluidly to an implanted catheter, to oneor more sources or bags of fresh dialysate and to a fluid drain.

The APD machines pump fresh dialysate from the dialysate source, throughthe catheter, into the patient's peritoneal cavity and allow thedialysate to dwell within the cavity so that the transfer of waste,toxins and excess water from the patient's bloodstream to the dialysatesolution can take place. The APD machines then pump spent dialysate fromthe peritoneal cavity, though the catheter, to the drain. APD machinesare typically computer controlled so that the dialysis treatment occursautomatically when the patient is connected to the dialysis machine, forexample, when the patient sleeps. That is, the APD systems automaticallyand sequentially pump fluid into the peritoneal cavity, allow for adwell, pump fluid out of the peritoneal cavity and repeat the procedure.As with the manual process, several drain, fill, and dwell cycles willoccur during APD. A “last fill” is typically used at the end of APD,which remains in the peritoneal cavity of the patient when the patientdisconnects from the dialysis machine for the day.

For both APD and CAPD it is desirable to optimize dwell time such thatthe dialysis solution remains inside the patient for as long as thefluid is efficiently absorbing waste or ultrafiltration (“UF”). When thedischarge fluid becomes “spent”, that is, it is not efficientlyabsorbing waste or UF, the dwell should be ended and a drain of thespent fluid should begin. It is desirable, especially for CAPD, to havea way to control the dwell time to be the optimized time and to notifythe patient the dwell time has expired. In the case of APD, suchinformation is also useful especially when the patient has disconnectedhimself or herself from the APD machine.

SUMMARY

The present disclosure sets forth an apparatus and method fordetermining, indicating and controlling an end of a patient dwell periodfor peritoneal dialysis (“PD”). The apparatus and method may be used tocontrol an APD machine and is especially useful with CAPD. In general, amaterial is used, such as a hydrogel material, which increases in volumein a controlled and predictable way as the material absorbs water ordialysis fluid over time. The polymer material or hydrogel absorbs theliquid causing the material to expand predictability. The exterior ofthe material is fitted with an electrical contact or contacts. As thematerial expands, the contact moves outwardly. Eventually the contact ismoved enough, such that it contacts a stationary contact. The materialis specifically configured such that the duration of the expansion upuntil the contacts mate coincides with the patient's optimal dwell time.

Once the contacts are mated, a circuit is completed and a signal isdelivered to an APD machine, which can signal a switch from a dwellphase to a drain phase. Alternatively, the contact closure sounds analarm or alert to a patient performing CAPD. The alert tells the CAPDpatient to end a dwell phase and begin draining. The apparatus thereforeacts as a timer to time out an optimal dwell, without the need for apower source for its movement.

The hydrogel material needs to be in contact with fluid over the courseof treatment. It is contemplated to place the hydrogel apparatus in thepatient line or in combination with the patient's transfer set, so thatfresh fluid remains in contact with the material during the entiredwell. In an APD application, the apparatus may be incorporated with adisposable cassette assuming that at least the apparatus associatedportion of the cassette remains primed during the entire dwell.

The timing of the apparatus is controlled via a number of parameters,such as, material type, porosity or percent open, and size. For example,a certain polymer hydrogel material may swell more quickly than otherpolymer hydrogels. A hydrogel that is more open than another hydrogelmay swell more quickly. A hydrogel material that is larger than anotherhydrogel material may swell more slowly because it requires more waterto become saturated.

In an alternative embodiment, the electrical contact is not a physicalcontact. For example, the hydrogel material could be configured tochange a capacitance (“ΔC”) between two parallel (or concentric) platesto form a parallel plate capacitor. As the hydrogel material hydrates,the distance between capacitor plates decreases and the resultingcapacitance increases.

It is accordingly an advantage of the present disclosure to provide adevice and method for optimizing a dwell period for peritoneal dialysis.

It is another advantage of the present disclosure to provide a deviceand method that times out or alarms or alerts when a patient's dwellperiod has ended.

It is a further advantage of the present disclosure to provide a dwellperiod timer or alerting apparatus that does not require external powerfor its movement.

It is still another advantage of the present disclosure to provide dwellperiod timer or alerting apparatus that can be incorporated readily intoa CAPD or APD disposable and sterilized via a preferred method.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of a disposable pumping and valvecassette, which houses a volume increasing material control switch ortimer of the present disclosure.

FIG. 2 is a schematic illustration of a patient line showing a patienttransfer set and an embodiment of a volume increasing material controlswitch or timer of the present disclosure.

FIG. 3 illustrates a patient's supply line having a patient transfer setthat incorporates an embodiment of the volume increasing materialcontrol switch or timer of the present disclosure.

FIG. 4 is a perspective view of one embodiment of the present disclosurein which the volume increasing material control switch is incorporatedinto a cap on the end of a supply line, wherein the cap is transferredto the patient's transfer set after fill.

FIGS. 5A and 5B are schematic sectioned views illustrating oneembodiment of a volume increasing material control switch or timer ofthe present disclosure in unactivated and activated conditions,respectively.

FIGS. 6A and 6B are schematic sectioned views illustrating a secondembodiment of a volume increasing material control switch or timer ofthe present disclosure in unactivated and activated conditions,respectively.

FIG. 7 is a schematic sectioned view of a further alternative embodimentof a volume increasing material control switch or timer of the presentdisclosure.

DETAILED DESCRIPTION

Referring now to the drawings and in particular to FIGS. 1 to 4, thevolume increasing material control apparatus of the present disclosure,denoted generally as apparatus 10, may be placed in a number of placesin an automated peritoneal dialysis (“APD”) disposable or continuousambulatory peritoneal dialysis (“CAPD”) disposable set. It isaccordingly contemplated to use apparatus 10 in connection with APD andCAPD. It should be appreciated however, that apparatus 10 is not limitedto peritoneal dialysis and may have application in hemodialysis or otherrenal blood treating system. Further alternatively, apparatus 10 may beused with other medical fluid systems and applications.

FIG. 1 illustrates apparatus 10 incorporated into a disposable pumpingand valving cassette 20. Pumping and valving cassettes are known in theart. One suitable cassette for integration with volume increasingmaterial apparatus 10 is disclosed in U.S. Pat. No. 5,350,357, thepertinent contents of which incorporated herein by reference. Generally,cassette 20 includes a pair of pumping chambers 22 a and 22 b thatcommunicate fluidly with a plurality of valve chambers 24 a to 24 h,which separate pump chambers 22 a and 22 b from a plurality of ports 26a to 26 d and from apparatus 10. Port 26 a is a drain port to which adrain line carries spent dialysate from cassette 20 to a house drain ordrain container. Ports 26 b to 26 d are supply ports that connect tosupply lines that lead to different supplies of dialysis fluid ordialysate. Port 26 e is a heater port that connects to a heater linethat extends to a heater bag. Pumps 22 a and 22 b pump fluid to theheater, which heats dialysate, after which the pumps pull heated fluidfrom the heater bag and push the heated fluid towards patient port 26 fthrough apparatus 10.

Pumps 22 a and 22 b fill the patient through apparatus 10, port 26 f anda patient line, which extends to a patient's peritoneum (or typically toa transfer set connected to the patient). Once the patient is filledwith fluid, valve chamber 24 h is closed, such that apparatus 10 remainsfilled with fluid. Apparatus 10 includes a volume increasing material,such as a hydrogel discussed in detail below, which becomes swollen orswells over time as fluid remains within apparatus 10.

FIG. 1 shows an application in which apparatus 10 is used to performAPD. FIGS. 2 through 4 illustrate applications in which apparatus 10 isused with an APD or a CAPD therapy. FIG. 2 illustrates a fill line 30,which runs to either patient port 26 f or cassette 20 of FIG. 1 for APDor to a supply bag for CAPD. Fill line 30 connects to a patient transferset 32, which has a disposable portion 32 a located at the end of fillline 30 and a reused patient port 32 b, connected to a patient catheterline 34, which extends to an indwelling catheter that extends inside thepatient's peritoneal cavity. The patient thus connects disposableportion 32 a to patient portion 32 b of transfer set 32 to establishfluid communication between cassette 20 or a fresh fluid source and thepatient. In FIG. 2, apparatus 10 is placed in fill line 30. The therapyis controlled such that fill line 30 is always full during dwell so thatapparatus 10 continues to be filled with dialysate even after thepatient's peritoneum is full. Fill line 30 either remains connected totransfer set 32 during dwell or is disconnected from the transfer setwhile full and clamped. In either case, a volume increasing materialplaced within apparatus 10 is constantly contacted by fluid. Indeed forboth the embodiments of FIGS. 1 and 2, the patient can place a clamp online 30 near connector 32 a or can alternatively cap connector 32 a tohold fluid within fill line 30, so that the fluid remains in contactwith the volume increasing material placed within apparatus 10.

In FIG. 3, apparatus 10 is incorporated into transfer set 32. FIG. 3shows apparatus 10 incorporated into the patient portion 32 b oftransfer set 32, such that apparatus 10 is reused. Alternatively,apparatus 10 is placed within disposable section 32 a of transfer set32, such that apparatus 10 is not reused. In certain PD applications,especially in connection with CAPD, which may be performed during theday, the patient disconnects disposable transfer set portion 32 a frompatent transfer set portion 32 b. Transfer set portion 34 b includes anintegrated twist clamp that the patient can close before disconnection.Such twist clamp seals the fluid so that it remains in contact withapparatus 10 in the embodiment of FIG. 3.

FIG. 4 illustrates one preferred embodiment of the present disclosure.Here, apparatus 10 is fitted at the end of fill line 30 with a cap 12.Apparatus is mated removeably and resealably with a connector 14, whichis fixed in sealed engagement with fill line 30. For example, connector14 can have a male luer tip (not illustrated) that is inserted through aresealable septum located at the proximal (or fill line 30) end ofapparatus 10. When connector 14 and fill line 30 are removed fromapparatus 10, the septum reseals the end of apparatus 10.

In FIG. 4, transfer set 32 is fitted with a removable cap 36. The distalend of apparatus 10 is configured to removeably and sealingly mate withthe connecting end (not seen in FIG. 4) of transfer set 40, e.g., via athreaded or sealed luer connection. When caps 12 and 32 are removed fromapparatus 10 and transfer set 32, the user or patient releasably andsealingly connects apparatus 10 to transfer set 32. Thereafter, thepatient is filled via a supply of dialysis fluid, through fill line 30,through connector 14, through apparatus 10, through transfer set 32,through patient line 14, and into the patient. The fill volume is enoughto maintain fluid contact with apparatus 10 at all times during andafter patient filling, so as to provide an accurate indicator of howlong the fluid has been delivered to the patient. Once the fill iscompleted, connector 14 is removed from apparatus 10, at which timeapparatus 10 reseals itself.

When apparatus 10 indicates that the dwell time for the previous fillhas elapsed, the patient can either connect/insert a drain line to/intoapparatus 10 or remove apparatus 10 and connect the drain line directlyto transfer set 32. Eventually, apparatus is removed from transfer set32 and is discarded. The next fill will be supplied using a new supplycontainer, new fill line 30 and a new apparatus 10 with cap 12 andconnector 14.

Referring now to FIGS. 5A and 5B, apparatus 10 a illustrates oneembodiment for apparatus 10 shown generally in FIGS. 1 to 4. Apparatus10 a includes a housing 40 having an input port 42 a and an output port42 b. For purposes of illustration, ports 42 a and 42 b are shownconnected fluidly to fill line 30 or patient catheter line 34, inconnection with the application embodiments of FIGS. 2 and 4,respectively. It should be appreciated however that apparatus 10 a canoperate alternatively with cassette 20 of FIG. 1 or with transfer set 32as shown in FIG. 3. In either case, apparatus 10 a may or may notrequire ports, such as ports 42 a and 42 b. Housing 40 is made of asuitable medical grade plastic, such as medical grade polyvinyl-chloride(“PVC”) or a medical grade non-PVC plastic, such as silicone.

Housing 40 also carries or forms a chamber 44 that houses a volumeincreasing material 50, such as a hydrogel. Either one or both ofchamber 44 and hydrogel material 50 may have a collar shape thatencircles a central axis through housing 40.

Hydrogel material 50 is in general a network of polymer chains that arewater insoluble. Hydrogel material 50 is a highly absorbent, natural orsynthetic polymer that may absorb over ninety-nine percent water.Hydrogels are also typically flexible and can be formed into a desiredshape. One suitable material for hydrogel 50 is described in U.S. Pat.No. 6,878,384, entitled, “Hydrogels That Undergo Volumetric Expansion InResponse To Changes In Their Environment And Their Methods OfManufacture And Use”, assigned to MicroVention, Inc. (Aliso Viego,Calif.), the entire contents of which are incorporated herein byreference and relied upon.

Chamber 44 includes a water permeable membrane or mesh 46 that allowsliquid, such as dialysis fluid, to permeate through surface 46 andcontact hydrogel material 50. In an embodiment, hydrogel material 50seals to permeable surface 46, such that water cannot fill withinchamber 44 to create fluid communication between a pair of contacts 48 aand 48 b located along an outer surface of chamber 44. A contact 52 islikewise placed along an outer surface of volume increasing or hydrogelmaterial 50. FIG. 5A shows an initial position, for example at thebeginning of a patient dwell, in which contact 52 on material 50 doesnot contact create electrical continuity between contact 48 a and 48 b.In FIG. 5B, for example at the end of a desired patient dwell, material50 has swollen or increased in volume, such that contact 52 now makesphysical contact with contacts 48 a and 48 b, thus completing anelectrical circuit 60 provided by apparatus 10 a.

Electrical circuit 60 includes a power supply 62, that powers an outputdevice 64 via an electrical line 66. In an embodiment, power supply 62is a DC battery supply, such as a rechargeable battery. Electrical line66 can be actual wire or a trace provided on a printed circuit board.Output device 64 can be a sonic and/or optical output device that forexample alerts a CAPD patient when an optimal dwell time has beencompleted, which coincides with the mating of contact 54 with contacts48 a and 48 b. In a CAPD example, the flashing light or audible sound atoutput device 64 causes the patient to begin the patient drain manually.

Output device 64 is alternatively a wireless transmitter or transceiverthat sends a wireless signal to a receiver or transceiver located on orat the APD machine. Here, apparatus 10 a sends a signal to the APDmachine informing the machine that the optimal dwell has ended, whichagain coincides with the mating of contact 52 with contacts 48 a and 48b. The signal sent from transmitter or transceiver 64 is processed atthe APD machine, which in turn causes a patient to drain to begin, forexample. In a further alternative embodiment, electrical line 66 ofcircuit 60 may extend to the APD device, such that the contact closurecan be sensed at the APD machine, upon which appropriate action istaken.

As discussed above, each patient has different physiologicalcharacteristics and responds to therapy in the patient's own way.Patients are typically categorized into four different transport modes,such as high, high-average, low and low-average. These transport modesin combination with therapy parameters, such as type of solution used,volume of solution used and other factors affects the overall dialysisperformance. U.S. patent application Ser. No. 12/431,458, entitled“Optimizing Therapy Outcomes For Peritoneal Dialysis”, filed Apr. 27,2009, assigned to the assignee of the present disclosure, the entirecontents of which are incorporated herein by reference sets forth anapparatus and method for determining the patient's optimal dwell timefor a given set of therapy parameters and based on the patient'sphysical characteristics and response to treatment.

Once that optimal dwell time is known, it is contemplated to structureexpanding volume material 50, such that it expands at a rate so thatcontact 52 engages contacts 48 a and 48 b at or near the optimal dwelltime ending duration. It is contemplated to vary the type of polymerused for material 50. It is further contemplated to vary the amount ofopenness or porosity of material 50.

Still further, it is contemplated to vary the size or thickness formaterial 50 based on the optimal dwell time. For example, in FIG. 5A anarrower hydrogel 50 will have more space to consume and thus may beused to indicate a longer dwell period. Alternatively, an inner diameterof material 50 (assuming it is collar shaped) can be reduced, such thatthe wall thickness of the collar increased for a given outside diameterof the collar. This could increase the amount of material that needs tobe saturated for expansion, which would also slow the expansion processand be used for a longer dwell duration.

The above variables are tested experimentally to derive a combinationthat yields a particular dwell time. The patient's optimal dwell time isthen matched with a like dwell time of a particular combination ofvariables for material 50.

While apparatus 10 a is shown with material 50 having an electricalcontact 52, it is contemplated that a highly fluid absorbed material 50may be conductive enough to create a repeatable and sensitive electricalcontinuity between contact 48 a and 48 b, such that material contact 52is not needed or used. For example, hydrogel material 50 itself may forman electrode comprised of a polyethylene oxide or polyvinyl pyrrolidone.

Referring now to FIGS. 6A and 6B, apparatus 10 b illustrates anotherembodiment for apparatus 10 shown generally in FIGS. 1 to 4. Here,housing 40 includes internal sidewall 45 that encases hydrogel material50 except for its inner surface. In an embodiment, hydrogel material 50seals to inner surfaces of walls 45, such that dialysis fluid cannottravel around material 50 and engage contact 48 a and 48 b to falselycreate electrical continuity. Contacts 48 a and 48 b in this alternativeembodiment are placed on the inside surface of housing 40. Power supply62, output device 64, electrical lines 66 of circuit 60 as discussedabove (including all alternatives) are used again for apparatus 10 b ofFIGS. 6A and 6B. An additional set of contacts 68 a and 68 b is providedthat pierce the wall of housing 40 to electrically connect innerelectrodes 48 a and 48 b with output device 64.

FIG. 6B illustrates that apparatus 10 b operates in a very similarmanner as apparatus 10 a. At a desired end of a dwell duration, hydrogelmaterial 50 is configured such that it has expanded, so that electricalcontinuity begins to exist between contacts 48 a and 48 b and likewisecontacts 68 a and 68 b. A separate electrode 52 may or may not be placedon an outer surface of hydrogel material 50 as has been discussedherein.

Referring now to FIG. 7, apparatus 10 c illustrates a furtheralternative embodiment for apparatus 10 shown in FIGS. 1 to 4. Apparatus10 c includes sidewalls 45, similar to those of FIGS. 6A and 6B, whichalong with a perforated bottom wall 46 support expanding polymer orhydrogel material 50. Hydrogel material 50 is coated on its outersurface with a colored marker, such as an opaque black, red, green orother suitable color marker. Housing 40 seals a transparent ortranslucent window 65, such as a plastic or glass window. The sizeand/or brightness of marker 54 are/is configured such that marker 54 isnot viewable (or not as viewable) until it reaches window 65. Apparatus10 c is accordingly a purely mechanical apparatus and does not require apower supply. Apparatus 10 c may be better suited for CAPD and/or for asingle fill version of apparatus 10, such as that of FIG. 4.

In still another alternative embodiment for apparatus 10 shown generallyin FIGS. 1 to 4, a physical electrical contact does not take place. Forexample, the hydrogel material could be configured to change acapacitance (“ΔC”) between two parallel (or concentric) plates to form aparallel plate capacitor. The capacitance is modeled by C=E*ε_(o)*A/d,where E is the magnitude of the electric field between two parallelplates separated by distance d, ε_(o) is the permittivity of free spaceand a constant equal to 8.85×10⁻¹² F/m, and A is the cross-sectionalarea of one of the plates. As the hydrogel material hydrates, ddecreases and capacitance C increases.

Aspects of the subject matter described herein may be useful alone or incombination one or more other aspect described herein. Without limitingthe foregoing description, in a first aspect of the present disclosure,a dialysis apparatus includes: a housing; a first electrical contactcarried by the housing; a hydrogel material located within the housing;a second electrical contact connected to the hydrogel material, thehydrogel material located so as to be contacted by a liquid flowingthrough the housing; and wherein the hydrogel material expands as thematerial absorbs the liquid such that the second electrical contact ismoved and eventually engage the first electrical contact.

In accordance with a second aspect of the present disclosure, which maybe used in combination with the first aspect, the engagement of thefirst and second contacts completes an electrical circuit.

In accordance with a third aspect of the present disclosure, which maybe used in combination with the second aspect, the electrical circuitincludes an alarm or alerting device that is activated upon theengagement of the first and second contacts.

In accordance with a fourth aspect of the present disclosure, which maybe used in combination with the second aspect, the electrical circuit isbattery powered.

In accordance with a fifth aspect of the present disclosure, which maybe used in combination with any one or more of the preceding aspects,the engagement of the first and second contacts signals an end of adialysate dwell period.

In accordance with a sixth aspect of the present disclosure, which maybe used in combination with any one or more of the preceding aspects,the first electrical contact is located on an inner wall of the housing,while the second electrical contact is located on an outer wall of thehydrogel material.

In accordance with a seventh aspect of the present disclosure, which maybe used in combination with any one or more of the preceding aspects,the liquid is a dialysis fluid.

In accordance with an eighth aspect of the present disclosure, which maybe used in combination with any one or more of the preceding aspects,the dialysis apparatus is used with (i) an automated peritoneal dialysis(“APD”) machine or with (ii) a continuous ambulatory peritoneal dialysis(“CAPD”) disposable set.

In accordance with a ninth aspect of the present disclosure, which maybe used in combination with any one or more of the preceding aspects,the dialysis apparatus is (i) located in a patient supply line, (ii)incorporated into a disposable cassette, (iii) incorporated into apatient's transfer set, and (iv) located in a section of tubing leadingfrom the patient's transfer set to the patient.

In accordance with a tenth aspect of the present disclosure, which maybe used in combination with any one or more of the preceding aspects,the hydrogel material is carried by the housing via a member permeableto the liquid.

In accordance with an eleventh aspect of the present disclosure, whichmay be used in combination with any one or more of the precedingaspects, the first contact includes a pair of contacts, which are placedin electrical or mechanical communication when the second contactengages the first contact.

In accordance with a twelfth aspect of the present disclosure, which maybe used in combination with any one or more of the preceding aspects, adialysis apparatus includes: a housing; first and second contactscovered by the housing; a material located within the housing; and athird electrical contact connected to the material, the material locatedso as to be contacted by liquid traveling through the housing, and thematerial configured to expand as the material absorbs the liquid suchthat the third contact moves into engagement with the first and secondcontacts.

In accordance with a thirteenth aspect of the present disclosure, whichmay be used in combination with any one or more of the preceding aspectsand the twelfth aspect, the material is a hydrogel material.

In accordance with a fourteenth aspect of the present disclosure, whichmay be used in combination with any one or more of the preceding aspectsand the twelfth aspect, the material is configured such that theengagement of the third contact with the first and second contactsoccurs at approximately an end of an optimal dwell duration for apatient.

In accordance with a fifteenth aspect of the present disclosure, whichmay be used in combination with any one or more of the preceding aspectsand the twelfth aspect, wherein at least one of: (i) a type, (ii) aporosity, and (iii) a size of the material is varied to set a particulartime needed for the third contact to move into engagement with the firstand second contacts.

In accordance with a sixteenth aspect of the present disclosure, whichmay be used in combination with any one or more of the precedingaspects, a dialysis method includes: filling a patient with dialysisfluid, such that the dialysis fluid remains in contact with a material;allowing the material to swell with dialysis fluid to a certain extent;and indicating that a patient dwell phase should be ended when thematerial has swollen to the certain extent.

In accordance with a seventeenth aspect of the present disclosure, whichmay be used in combination with any one or more of the preceding aspectsand the sixteenth aspect, wherein the dialysis method includes choosingthe material such that a duration needed for the material to swell tothe certain extent coincides with an optimal dwell time for the patient.

In accordance with an eighteenth aspect of the present disclosure, whichmay be used in combination with any one or more of the preceding aspectsand the sixteenth aspect, wherein the dialysis method includesmechanically indicating that the patient dwell phase should be ended.

In accordance with a nineteenth aspect of the present disclosure, whichmay be used in combination with any one or more of the preceding aspectsand the sixteenth aspect, wherein the dialysis method includeselectrically, audibly or visually indicating that the patient dwellphase should be ended.

In accordance with a twentieth aspect of the present disclosure, whichmay be used in combination with any one or more of the preceding aspectsand the sixteenth aspect, wherein the dialysis method includes locatingthe material in an apparatus that is transferred from a supply fill lineto a transfer set worn by the patient.

In accordance with a twenty-first aspect of the present disclosure,which may be used in combination with any one or more of the precedingaspects and the sixteenth aspect, wherein the dialysis method includescapacitively determining that the material has swollen to the certainextent.

In accordance with a twenty-second aspect of the present disclosure, anyof the structure and functionality illustrated and described inconnection with FIG. 1 may be used in combination with any one or moreof the preceding aspects.

In accordance with a twenty-third aspect of the present disclosure, anyof the structure and functionality illustrated and described inconnection with FIG. 2 may be used in combination with any one or moreof the preceding aspects.

In accordance with a twenty-fourth aspect of the present disclosure, anyof the structure and functionality illustrated and described inconnection with FIG. 3 may be used in combination with any one or moreof the preceding aspects.

In accordance with a twenty-fifth aspect of the present disclosure, anyof the structure and functionality illustrated and described inconnection with FIG. 4 may be used in combination with any one or moreof the preceding aspects.

In accordance with a twenty-sixth aspect of the present disclosure, anyof the structure and functionality illustrated and described inconnection with FIGS. 5A and 5B may be used in combination with any oneor more of the preceding aspects.

In accordance with a twenty-seventh aspect of the present disclosure,any of the structure and functionality illustrated and described inconnection with FIGS. 6A and 6B may be used in combination with any oneor more of the preceding aspects.

In accordance with a twenty-eighth aspect of the present disclosure, anyof the structure and functionality illustrated and described inconnection with FIG. 7 may be used in combination with any one or moreof the preceding aspects.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A dialysis system comprising: a dialysis machine or a dialysisdisposable set; and an apparatus operable with the dialysis machine orthe dialysis disposable set, the apparatus including: a housing; a firstelectrical contact carried by the housing; a hydrogel material locatedwithin the housing; a second electrical contact connected to thehydrogel material, the hydrogel material located so as to be contactedby a liquid flowing through the housing; and wherein the hydrogelmaterial expands as the material absorbs the liquid such that the secondelectrical contact is moved and eventually engages the first electricalcontact.
 2. The dialysis system of claim 1, wherein the engagement ofthe first and second contacts completes an electrical circuit.
 3. Thedialysis system of claim 2, wherein the electrical circuit includes analarm or alerting device that is activated upon the engagement of thefirst and second contacts.
 4. The dialysis system of claim 2, whereinthe electrical circuit is battery powered.
 5. The dialysis system ofclaim 1, wherein the engagement of the first and second contacts signalsan end of a dialysate dwell period of a dialysis treatment performed bythe machine or by a patient.
 6. The dialysis system of claim 1, whereinthe first electrical contact is located on an inner wall of the housing,while the second electrical contact is located on an outer wall of thehydrogel material.
 7. The dialysis system of claim 1, wherein the liquidis a dialysis fluid.
 8. The dialysis system of claim 1, wherein thedialysis machine includes an automated peritoneal dialysis (“APD”)machine and the dialysis disposable set includes a continuous ambulatoryperitoneal dialysis (“CAPD”) disposable set.
 9. The dialysis system ofclaim 1, wherein the apparatus is (i) located in a patient supply line,(ii) incorporated into a disposable cassette; (iii) incorporated into apatient's transfer set, and (iv) located in a section of tubing leadingfrom the patient's transfer set to the patient.
 10. The dialysis systemof claim 1, wherein the hydrogel material is carried by the housing viaa member permeable to the liquid.
 11. The dialysis system of claim 1,wherein the first contact includes a pair of contacts, which are placedin electrical or mechanical communication when the second contactengages the first contact.
 12. A dialysis system comprising: a dialysismachine or a dialysis disposable set; and an apparatus operable with thedialysis machine or the dialysis disposable set, the apparatusincluding: a housing; first and second contacts covered by the housing;a material located within the housing; and a third electrical contactconnected to the material, the material located so as to be contacted byliquid traveling through the housing, and the material configured toexpand as the material absorbs the liquid such that the third contactmoves into engagement with the first and second contacts.
 13. Thedialysis system of claim 12, wherein the material is a hydrogelmaterial.
 14. The dialysis system of claim 12, wherein the material isconfigured such that the engagement of the third contact with the firstand second contacts occurs at approximately an end of an optimal dwellduration for a patient of a dialysis treatment performed by the machineor by the patient.
 15. The dialysis system of claim 12, wherein at leastone of: (i) a type, (ii) a porosity, and (iii) a size of the material isvaried to set a particular time needed for the third contact to moveinto engagement with the first and second contacts.